Filename: 001-process.txt
Title: The Tor Proposal Process
Author: Nick Mathewson
Created: 30-Jan-2007
Status: Meta

Overview:

   This document describes how to change the Tor specifications, how Tor
   proposals work, and the relationship between Tor proposals and the
   specifications.

   This is an informational document.

Motivation:

   Previously, our process for updating the Tor specifications was maximally
   informal: we'd patch the specification (sometimes forking first, and
   sometimes not), then discuss the patches, reach consensus, and implement
   the changes.

   This had a few problems.

   First, even at its most efficient, the old process would often have the
   spec out of sync with the code.  The worst cases were those where
   implementation was deferred: the spec and code could stay out of sync for
   versions at a time.

   Second, it was hard to participate in discussion, since you had to know
   which portions of the spec were a proposal, and which were already
   implemented.

   Third, it littered the specifications with too many inline comments.
     [This was a real problem -NM]
       [Especially when it went to multiple levels! -NM]
         [XXXX especially when they weren't signed and talked about that
          thing that you can't remember after a year]

How to change the specs now:

   First, somebody writes a proposal document.  It should describe the change
   that should be made in detail, and give some idea of how to implement it.
   Once it's fleshed out enough, it becomes a proposal.

   Like an RFC, every proposal gets a number.  Unlike RFCs, proposals can
   change over time and keep the same number, until they are finally
   accepted or rejected.  The history for each proposal
   will be stored in the Tor repository.

   Once a proposal is in the repository, we should discuss and improve it
   until we've reached consensus that it's a good idea, and that it's
   detailed enough to implement.  When this happens, we implement the
   proposal and incorporate it into the specifications.  Thus, the specs
   remain the canonical documentation for the Tor protocol: no proposal is
   ever the canonical documentation for an implemented feature.

   (This process is pretty similar to the Python Enhancement Process, with
   the major exception that Tor proposals get re-integrated into the specs
   after implementation, whereas PEPs _become_ the new spec.)

   {It's still okay to make small changes directly to the spec if the code
   can be
   written more or less immediately, or cosmetic changes if no code change is
   required.  This document reflects the current developers' _intent_, not
   a permanent promise to always use this process in the future: we reserve
   the right to get really excited and run off and implement something in a
   caffeine-or-m&m-fueled all-night hacking session.}

How new proposals get added:

  Once an idea has been proposed on the development list, a properly formatted
  (see below) draft exists, and rough consensus within the active development
  community exists that this idea warrants consideration, the proposal editors
  will officially add the proposal.

  To get your proposal in, send it to the tor-dev mailing list.

  The current proposal editors are Nick Mathewson, George Kadianakis,
  Damian Johnson, Isis Lovecruft, and David Goulet.

What should go in a proposal:

   Every proposal should have a header containing these fields:
     Filename, Title, Author, Created, Status.

   These fields are optional but recommended:
     Target, Implemented-In, Ticket**.

   The Target field should describe which version the proposal is hoped to be
   implemented in (if it's Open or Accepted).  The Implemented-In field
   should describe which version the proposal was implemented in (if it's
   Finished or Closed).  The Ticket field should be a ticket number referring
   to Tor's canonical bug tracker (e.g. "#7144" refers to
   https://bugs.torproject.org/7144) or to a publicly accessible URI where one
   may subscribe to updates and/or retrieve information on implementation
   status.

   ** Proposals with assigned numbers of prop#283 and higher are REQUIRED to
      have a Ticket field if the Status is OPEN, ACCEPTED, CLOSED, or FINISHED.

   The body of the proposal should start with an Overview section explaining
   what the proposal's about, what it does, and about what state it's in.

   After the Overview, the proposal becomes more free-form.  Depending on its
   length and complexity, the proposal can break into sections as
   appropriate, or follow a short discursive format.  Every proposal should
   contain at least the following information before it is "ACCEPTED",
   though the information does not need to be in sections with these names.

      Motivation: What problem is the proposal trying to solve?  Why does
        this problem matter?  If several approaches are possible, why take this
        one?

      Design: A high-level view of what the new or modified features are, how
        the new or modified features work, how they interoperate with each
        other, and how they interact with the rest of Tor.  This is the main
        body of the proposal.  Some proposals will start out with only a
        Motivation and a Design, and wait for a specification until the
        Design seems approximately right.

      Security implications: What effects the proposed changes might have on
        anonymity, how well understood these effects are, and so on.

      Specification: A detailed description of what needs to be added to the
        Tor specifications in order to implement the proposal.  This should
        be in about as much detail as the specifications will eventually
        contain: it should be possible for independent programmers to write
        mutually compatible implementations of the proposal based on its
        specifications.

      Compatibility: Will versions of Tor that follow the proposal be
        compatible with versions that do not?  If so, how will compatibility
        be achieved?  Generally, we try to not drop compatibility if at
        all possible; we haven't made a "flag day" change since May 2004,
        and we don't want to do another one.

      Implementation: If the proposal will be tricky to implement in Tor's
        current architecture, the document can contain some discussion of how
        to go about making it work.  Actual patches should go on public git
        branches, or be uploaded to trac.

      Performance and scalability notes: If the feature will have an effect
        on performance (in RAM, CPU, bandwidth) or scalability, there should
        be some analysis on how significant this effect will be, so that we
        can avoid really expensive performance regressions, and so we can
        avoid wasting time on insignificant gains.

Proposal status:

   Open: A proposal under discussion.

   Accepted: The proposal is complete, and we intend to implement it.
      After this point, substantive changes to the proposal should be
      avoided, and regarded as a sign of the process having failed
      somewhere.

   Finished: The proposal has been accepted and implemented.  After this
      point, the proposal should not be changed.

   Closed: The proposal has been accepted, implemented, and merged into the
      main specification documents.  The proposal should not be changed after
      this point.

   Rejected: We're not going to implement the feature as described here,
      though we might do some other version.  See comments in the document
      for details.  The proposal should not be changed after this point;
      to bring up some other version of the idea, write a new proposal.

   Draft: This isn't a complete proposal yet; there are definite missing
      pieces.  Please don't add any new proposals with this status; put them
      in the "ideas" sub-directory instead.

   Needs-Revision: The idea for the proposal is a good one, but the proposal
      as it stands has serious problems that keep it from being accepted.
      See comments in the document for details.

   Dead: The proposal hasn't been touched in a long time, and it doesn't look
      like anybody is going to complete it soon.  It can become "Open" again
      if it gets a new proponent.

   Needs-Research: There are research problems that need to be solved before
      it's clear whether the proposal is a good idea.

   Meta: This is not a proposal, but a document about proposals.

   Reserve: This proposal is not something we're currently planning to
      implement, but we might want to resurrect it some day if we decide to
      do something like what it proposes.

   Informational: This proposal is the last word on what it's doing.
      It isn't going to turn into a spec unless somebody copy-and-pastes
      it into a new spec for a new subsystem.

   Obsolete: This proposal was flawed and has been superseded by another
     proposal. See comments in the document for details.

   The editors maintain the correct status of proposals, based on rough
   consensus and their own discretion.

Proposal numbering:

   Numbers 000-099 are reserved for special and meta-proposals.  100 and up
   are used for actual proposals.  Numbers aren't recycled.
